While in vitro models can provide insight into many aspects of viral infection, in vivo models are critical to the understanding of the pathogenesis and treatment of viral diseases. The recent development and use of animal models that display pathology following infection with human immunodeficiency virus type 1 (HIV-1) has significantly expanded our knowledge of the mechanisms associated with viral pathogenesis and provided an impetus towards the development of therapeutic approaches. The development of humanized mouse models has provided novel model systems with which to study the human immune system and the effects of HIV infection on human cells and tissues. These models involve transplantation of various types of human tissues into mice who possess one or more of several types of immune defects. The human tissue can then engraft, grow and develop in a similar fashion as it would in humans, allowing the study of this tissue in a living system. The human tissue used in these studies is capable of a high degree of manipulation and experimentation in the mouse and the human cells, versus the mouse cells, are further susceptible to infection with HIV. This provides a powerful model to examine human bloods cell development, to study the effects of HIV infection on human cells, and ways to protect the human immune system from HIV. The generation of these humanized mice is a highly specialized procedure, due to the requirement for immunodeficient mouse strains, human hematopoietic tissue, infectious material, specialized facilities, and the necessary skill and knowledge to perform experiments in this system. The CFAR supported Humanized Mouse Core is designed to assist AIDS-related investigators at UCLA with their research by providing all of the resources and the environments necessary to support the use of state-of-the art humanized mouse technologies. This facility will support the use of humanized mice for AIDS-related research under both Biosafety Level 2 and Biosafety Level 2+ conditions. This facility will also provide consultation on the use of humanized mouse models, as well as construct various humanized animals for distribution to Core users. Thus, the overall goal of this Core laboratory is to provide the infrastructure, materials, animals, technical expertise and support that will facilitate the use of humanized immunodeficient mice in AIDS-related studies.